This invention relates generally to optical systems and more particularly, to methods and apparatus for measuring an opening area defined within a flow nozzle.
At least some known gas turbine engines include a compressor, a combustor, and at least one turbine coupled in a serial axial-flow relationship. The compressor compresses air which is then channeled to the combustor. The compressed air is mixed with fuel and ignited within the combustor to generate combustion gases which are channeled to the turbine. The turbine extracts energy from the combustion gases to power the compressor, as well as to produce useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
A nozzle throat area of the engine is a critical parameter affecting engine efficiency. Accordingly, the nozzle throat area is measured during periodic inspections to verify clearances in the engine fluid path. New nozzle throats are carefully designed to provide a specific area value. Accurately measuring an opening area of the nozzle may also be relevant in determining a manufacturing time of the nozzle, as well as subsequent maintenance and repair costs and activities.
Conventional nozzle throat inspection methods include using a mechanical gauge. At least one known mechanical gauge includes a complex mechanical analog computer that multiplies a width of the throat by a height measured at several specified locations. Another known area gauge uses electronic linear voltage differential transformer (LVDT) sensors to measure the throat width and height values, and then a computer calculates the area. However, obtaining accurate measurements at the various orientations of the nozzle throat may be a difficult task. Furthermore, because of the contours and dimensions of the nozzle throat, using such gauges may be a costly and time-consuming process.